This invention relates to a method for handling business forms, and more particularly, to a method which zig-zag folds at least three webs separately in side-by-side relation. As such, it constitutes an improvement upon my earlier U.S. Pat. No. 3,596,899.
In that patent, a method of producing web units was disclosed wherein at least two webs were superposed for simultaneous processing and thereafter laterally separated for zig-zag folding. The method of this prior patent was an improvement over machines which had both two-wide processing and folding in that it eliminated the need for greater diameter printing press cylinders, which in turn necessitated additional plates, thereby creating problems of register. Also the U.S. Pat. No. 3,596,899 was an improvement over the prior tandem machines (2 single width folders in line) which required one operator at each folder.
Although apparatus for performing the method of my prior patent has been known throughout the world since Oct. 1969 -- when it was demonstrated at an international exhibition in Milan, Italy, and notwithstanding the fact that the method has become highly successful commercially -- being practiced in over forty machines throughout the world (each operating at speeds of the order of 1000 feet per minute) no one has seen fit to apply the patented method to three or more webs. This is all the more startling when it is considered that with a modest investment in an additional two-wide folder, four webs can be produced whereas only two could be produced before -- and the finished product handled by the same artisan that previously handled the two folded webs. Thus there is possible an increase of 100% in production (and when this occurs at 1000 feet per minute, it seems strange that no one appreciated the instant invention). Also, even though 2 wide folders had been used by the industry for over 10 years, nobody arranged them in side-by-side relationship until this invention.
More importantly, the logical or obvious move to increase production over that available from the machine of the U.S. Pat. No. 3,596,899 was to go to a three-wide folder, i.e., moving a third web to the other or "unused" side of the basic path in the U.S. Pat. No. 3,596,899. This would be consistent with the prior art approach of having webs symmetrically disposed on both sides of the path. However, this obvious step would not achieve the goal of increased production.
The U.S. Pat. No. 3,596,899 machine was set up to run at 1000 feet per minute, and further can be rapidly changed over to run different web weights and patterns. For example, the tucker and gripper relationship of the folder has to be changed slightly -- even with the same repeat -- when the weights are changed, as from a 10 lb/ream to a 12 lb/ream web. The mechanism for doing this in a two-wide folder is relatively simple -- cams for closing the grippers being provided at each end of the folder, one each for the adjacent folder. However, with a three-wide folder, a fairly complicated internal mechanism is required for actuating and timing the movement of the grippers in the middle folder -- mechanism sufficiently complicated that the art has generally avoided three-wide folders. Also, use of a three-wide folder could result in a substantial reduction of speed because of the wider span (nominally 45 inches versus 30 inches -- the typical business form being 15 inches wide) would require lower speed operation to avoid vibration. Thus, the logical move would not only complicate the mechanism but, more importantly would not achieve the desired goal -- increased production. For example, if the speed of a three-wide folder had to be reduced 1/3 -- to 667 feet per minute compared to a two-wide folder set up, the three web production would still aggregate only 2,000 feet per minute -- just what was being produced on the U.S. Pat. No. 3,596,899 two-wide folder.
It was not obvious to go to two two-wide folders -- this based on the fact that the use of a second two-wide folder would require a substantial lateral shift of the third web -- of the order of 53 inches (35 inches gap between paper edges) as contrasted to about 20 inches (2 inches gap between paper edges) in the U.S. Pat. No. 3,596,899 machine. Admittedly, webs were shifted substantially in the prior art but not webs that were traveling at 1000 feet per minute and in the midst of processing. The contra-indication of going to a separate folder in the high speed operation of the U.S. Pat. No. 3,596,899 machine was borne out in the building of the machine according to the disclosure in this application. Several years were involved and after the machine was installed in the customer's plant, several months elapsed before the operation was proper.